No-tillage(NT)and straw return(S)collectively affect soil organic carbon(SOC).However,changes in the organic carbon pool have been under-investigated.Here,we assessed the quantity and quality of SOC after 11 years of tillage and straw return on the North China Plain.Concentrations of SOC and its labile fractions(particulate organic carbon(POC),potassium permanganate-oxidizable organic carbon(POXC),microbial biomass carbon(MBC),and dissolved organic carbon(DOC)),components of DOC by fluorescence spectroscopy combined with parallel factor analysis(PARAFAC),and the chemical composition of SOC by 13C NMR(nuclear magnetic resonance)spectroscopy were explored.Treatments comprised conventional tillage(CT)and NT under straw removal(S0),return of wheat straw only(S1),or return of both wheat straw and maize residue(S2).Straw return significantly increased the concentrations and stocks of SOC at 0-20 cm depth,but NT stratified them with enrichment at 0-10 cm and a decrease at 10-20 cm compared to CT,especially under S2.Labile C fractions showed similar patterns of variation to that of SOC,with POC and POXC more sensitive to straw return and the former more sensitive to tillage.Six fluorescence components of DOC were identified,mainly comprising humic-like substances with smaller amounts of fulvic acid-like substances and tryptophan.Straw return significantly decreased the fluorescence index(Fl)and autochthonous index(BIX)and increased the humification index(HIX).No-tillage generally increased HIX in topsoil but decreased it and increased the Fl and BIX below the topsoil.Relative abudance order of the chemical composition of SOC was:O-alkyl C＞alkyl-C＞aromatic-C＞carbonyl-C.Overall,NT under S2 effectively increased SOC and its labile C forms and DOC humification in topsoil and microbially-derived DOC below the topsoil.Return of both wheat and maize straw was a decisive factor in promoting SOC in the plow layer.The stratification of SOC under NT may confer a long-term influence on carbon sequestration.

LI Teng-teng;ZHANG Jiang-zhou;ZHANG Hong-yan;Peter CHRISITE;ZHANG Jun-ling

Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems&CAS Engineering Laboratory for Vegetation Ecosystem Restoration on Islands and Coastal Zones,South China Botanical Garden,Chinese Academy of Sciences(CAS),Guangzhou 510650,P.R.China;College of Resources and Environmental Sciences,China Agricultural University/National Academy of Agriculture Green Development/Key Laboratory of Plant-Soil Interactions,Ministry of Education,Beijing 100193,P.R.China;College of Resources and Environment/International Magnesium Institute,Fujian Agriculture and Forestry University,Fuzhou 350002,P.R.China

农业科学学报（英文）

[1]LI Teng-teng;ZHANG Jiang-zhou;ZHANG Hong-yan;Peter CHRISITE;ZHANG Jun-ling-.Fractionation of soil organic carbon in a calcareous soil after long-term tillage and straw residue management)[J].农业科学学报（英文）,2022(12):3611-3625

POXC,abudance,plow

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